Conventionally, in a manufacturing process of a semiconductor device, plasma processing is carried out to perform etching or deposition on a substrate such as a semiconductor wafer by the action of a plasma. In the manufacturing process of the semiconductor device, for example, in the manufacturing process of a NAND flash memory, it is known that plasma etching and trimming of a mask are performed on a multilayer film formed by alternately stacking two types of films having different dielectric constants, e.g., an insulating film and a conductive film to form a step-shaped structure (see, e.g., Patent Document 1).